EHV-1 Outbreak: Additional Cases Reported Over Weekend

More than two weeks after the conclusion of the National Cutting Horse Association's (NCHA) Western Regional Championships--held April 19-May 8 in Ogden, Utah--reports of equine herpesvirus-1 (EHV-1) confirmed cases continue to trickle in. The outbreak, believed to stem from horses that attended the NCHA competition, captured the collective attention of the horse industry last week after numerous facilities quarantined horses.

Equine herpesvirus-1 is highly contagious and can cause a variety of ailments in horses, including rhinopneumonitis (a respiratory disease usually found in young horses), abortion in broodmares, and myeloencephalopathy (the neurologic form). The virus is not transmissible to humans. Clinical signs of EHV-1 myeloencephalopathy (EHM) include fever, ataxia (incoordination), weakness or paralysis of the hind limbs, and incontinence. The virus is generally passed from horse to horse via aerosol transmission (when affected animals sneeze/cough) and contact with nasal secretions.

New Cases

California - One new case of confirmed EHV-1 had been reported in California as of noon today, according to the state's Department of Food and Agriculture. This brings the total number of confirmed cases to 18. There is only one related fatality thus far in California. A statement released by the department indicated that "seven positive horses have displayed neurological signs, 10 cases have displayed an increased temperature, and one horse has not displayed any clinical signs." The horses are located in the following counties: Glenn, Plumas, and Shasta in Northern California; Amador, Marin, Napa, Placer, and Sacramento in North Central California; Stanislaus in Central California; Kern in South Central California; and Los Angeles and Ventura in Southern California.

Utah - As of noon today, the Utah Department of Agriculture reported seven confirmed cases of EHV-1 and eight suspected cases located on four quarantined facilities in the following counties: Box Elder and Davis in Northwest Utah, Kane in Southwest Utah, and Utah in the central part of the state. Today's statement indicated that "two of the cases were humanely euthanized after going down and (being) unable to return to their feet." The clinical signs associated with the other confirmed or suspected cases were not noted.

Washington - The Washington Department of Agriculture reported an additional confirmed case of EHV-1 today, bringing the total to six. Two of the confirmed cases (both located at Washington State University's Veterinary Teaching Hospital) displayed only a fever. It is not known whether the remainder of the confirmed cases exhibited neurologic signs.

Colorado - A press release issued today by the state's Department of Agriculture indicated that there were nine confirmed cases of EHV-1 in Colorado and 22 suspected cases. Two of the horses with confirmed cases were euthanized after displaying severe neurologic signs, but it is not clear whether the remaining seven cases showed neurologic signs. There are 12 facilities under quarantine in the following counties: Bent in Southeast Colorado, Boulder and Larimer in North Central Colorado, Garfield and Mesa in Western Colorado, Gunnison in West Central Colorado, and Morgan and Weld in Northeast Colorado.

Oregon - A statement issued on the Oregon Department of Agriculture's website today noted an additional case of EHV-1 was confirmed. The state's EHV-1 case total is now three, and there are two additional horses awaiting diagnostic test results. The department reported that none of the cases displayed neurologic clinical signs. The horses are located in the following counties: Clackamas (Northwest Oregon), Umatilla (Northeast Oregon), and Deschutes (Central Oregon).

Holding Steady

Alberta's chief provincial veterinarian, Gerald Hauer, DVM, said today that he'd not heard of any new confirmed cases reported over the weekend. The total number of confirmed cases in the province stands at three (two of which had not displayed any neurologic signs).

Arizona, New Mexico, and Texas are reportedly holding steady at one case each, according to the regulatory bodies in each state. The Arizona and New Mexico horses each were euthanized after displaying neurologic signs. It is unclear whether the Texas horse exhibited neurologic signs or not.

State veterinarians are now reporting their confirmed and suspected cases to the USDA's Animal and Plant Health Inspection Service, which has begun to keep a tally of the number of cases nationwide.

EHV-1 in Florida Not Related to Outbreak

Two horses in Florida were euthanized last week after one tested positive for neurologic EHV-1 and one was suspected of having the disease. A report from the Florida Department of Agriculture & Consumer Service's Animal Industry Division indicated that state officials do not believe the two Florida cases are related to the outbreak in the western United States.

"In a separate incident we have one farm in Alachua County (located in Northern Florida), which is under state quarantine, that has had two horses euthanized due to complications of EHV-1 infection (one case suspected and one confirmed)," the release read. "We believe that the index case occurred on the quarantined farm due to reemergence of a latent infection and that no exposure has occurred off the affected premises."

A related report from the attending veterinary hospital--North Florida Equine Veterinary Service in Newberry--indicated this appeared to be an isolated occurrence: "It is true that a case of neurologic herpes was recently diagnosed in Alachua County. It was at a private farm not adjoining any other horse properties. Horses on the property had not been to other farms, show facilities, or clinics. In short, exposure was very limited."

About the Author

Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.

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